Dental, Dental-Medical or Dental-Technical Handpiece With Electric Motor

ABSTRACT

In a dental, dental-medical or dental-technical handpiece, having an elongate grip sleeve there are provided at the rearward end of the grip sleeve coupling elements for the connection of the handpiece to a supply hose to be connected with a dental supply arrangement, and there are provided at the forward end of the grip sleeve a head section with a tool receiver for mounting a tool to be put into rotation. The handpiece further has an electric motor for driving a tool held by the tool receiver, which motor is completely integrated into the grip sleeve such that grip sleeve and motor form a unit.

The present invention relates to a dental, dental-medical ordental-technical handpiece in accordance with the preamble of the claim1, which has an electric motor for driving a tool held by a toolreceiver of the handpiece, in particular a dental drill.

Dental or dental-medical handpieces normally include an instrumentsection for receiving a rotating dental tool, for example a drill, adrive motor for driving the dental tool, and a hose section with a mediadelivery hose for delivering certain supply media for the operation ofthe handpiece. Hereunder there fall for example current for operating anelectric motor and/or a light source, but also cooling media such as airand water.

FIGS. 11 and 12 show handpieces in accordance with the state of the artwhich are configured in different manners. As FIG. 11 shows, theinstrument section 101, the drive motor 103 and the hose section 102with the media delivery hose 104 can be configured as individualcomponents which can then be coupled directly behind one another byplugging on. This construction thus has three coupling points betweenthe instrument section 101 and the hose section 102, and respectivelybetween the drive motor 103 and the two sections 101 and 102. Such aconstruction for a handpiece is known for example from DE 28 34 099 C2or EP 0 012 871 B1.

A form of construction alternative to this for a dental ordental-medical handpiece is illustrated in FIG. 12. The drive motor 203is now a so-called motor cartridge which is kept in a cavity formed bythe instrument section 201 and the hose section 202. The instrumentsection has for this purpose a housing overlapping the drive motor 203with integrated supply lines for receiving the supply media delivered bythe media delivery hose, wherein the housing and the supply lines of theinstrument section 201 are led up to the hose section 202.

These two known forms of construction are problematic in multipleregards. Thus for example, due to the great structural length, dictatedby the form of construction, and the relatively great weight of thedental handpiece, handling is made more difficult since the center ofgravity is shifted towards the hose side. However, delicate and easyhandling is required precisely for dental work. Further, the manycoupling points or separation points between the components of thehandpiece are critical with regard to hygiene requirements.

To avoid these issues, correspondingly a new concept has been proposedin EP 0 888 091 A1, in which both the handpiece and the motor aredivided into two components. A first section of the handpiece therebyserves for receiving a dental tool and is releasably couplable with asecond section to which a medium supply line for the supply of certainsupply media for operation of the tool can be connected. In turn thedrive motor is divided into a rotating region and a static region with astator winding, wherein both parts are so respectively arranged in thetwo sections of the handpiece that through assembly of the first andsecond handpiece sections the static region of the drive motor with thestator winding is pushed over the rotating region of the drive motor. Inthis way on the one hand the structural length of the handpiece and onthe other hand the number of interfaces can be reduced in comparisonwith the concepts illustrated in FIGS. 11 and 12.

The present invention is based on the object of indicating a furtherimproved concept for a dental, dental-medical or dental-technicalhandpiece, which in comparison with the known configurations can be kepteven more compact and makes possible a further improved handling.

The object is achieved by a dental, dental-medical or dental-technicalhandpiece having the features of the claim 1. Advantageous developmentsof the invention are the subject of the dependent claims.

The solution in accordance with the invention is based on the use of newelectric motors which in comparison with earlier configurations areconfigured considerably more compactly and nevertheless are effective.It is proposed now to use such an electric motor for the operation of adental or dental-medical handpiece, whereby motor is preferably aso-called collectorless or brushless motor with a permanent magnetrotor, and to integrate this completely into an elongate grip sleeve ofthe handpiece.

In accordance with the present invention there is thus proposed adental, dental-medical or dental-technical handpiece which has anelongate grip sleeve, at the rearward end of which there are providedcoupling elements for the connection of the handpiece to a supply hoseto be connected with a dental supply facility, and at the forward end ofwhich there is arranged a head section having a tool receiver formounting a tool which is to be set into rotation. The handpiece hasfurther an electric motor for driving a tool held by the tool receiver,wherein in accordance with the invention it is provided that theelectric motor is integrated completely into the grip sleeve so that itforms a unit with this. The grip sleeve is here constituted in one piecein accordance with a particularly preferred embodiment or consists of aplurality of parts which are not separable for a user of the handpiece.

The advantages arising with the solution in accordance with theinvention are extremely various. Thus, firstly there is achieved ashortened structural form through the complete integration of theelectric motor into the grip sleeve of the handpiece, what leads toimproved ergonomics. This can be explained by a reduced weight for thehandpiece as well as smaller effective lever arms. A further advantageconsists in that motor speeds in a very broad range of 10,000-300,000rpm, preferably from 75,000-250,000 rpm, can be used, for which reasonthere can be used fewer and more simply configured transmission elementsfor transmission of the rotation movement. Overall, the number ofmechanical components for the transmission of movement can be reducedconsiderably with the solution in accordance with the invention, whichresults in better controllable production, low production costs as wellas improved maintenance friendliness. The hygiene of the handpiece isalso improved with the solution in accordance with the invention sincethe interfaces or couplings provided or required in the state of the artbetween a motor part and further handpiece components are omitted.Finally, the operating noise of the handpiece is also reduced, since themasses moved in operation are considerably less than in the handpiecesknown from the state of the art.

In accordance with an advantageous development of the present inventionthe grip sleeve is angled, whereby it can then be provided that the toolreceiver is connected with the motor via a shaft which extends throughthe forward region of the grip sleeve. This shaft can be coupled withthe shaft of the motor via a knee transmission; in turn at the forwardend a coupling with the tool receiver in the head section of thehandpiece can be effected via a head transmission. This headtransmission preferably causes a reversal of direction of rotation,wherein the motor then is controlled for counter-clockwise rotation.Here, it can further be provided that one of the transmissions effects atranslation which may lie in the region between 2:1 and 1:2.

The motor has preferably a max. speed of rotation of 250,000 rpm. Thehead section can be arranged, with regard to the forward end of thehandpiece, at an angle of about 100° , through which handling is furtherimproved.

Other developments of the invention concern in particular theconfiguration and mounting of the motor within the handpiece inaccordance with the invention. Here it is provided—as alreadymentioned—in accordance with an advantageous development of theinvention, that a collectorless or brushless dc motor (BLDC-Motor)having at least one rotating permanent magnets is put to use, whichdistinguishes itself due to its high efficiency. In order to be able toeffectively protect the sensitive components of this motor during theregularly needed sterilizing process required with such handpieces,there are now provided particular measures which are the subject offurther dependent claims.

Thus, firstly, the permanent magnet or magnets of the rotor can beprovided with a special coating which protects these from corrosion. Aprotection of the sensitive stator windings and the stator laminationscan, in contrast, be achieved in that the stator is surrounded by aplastic encasing or plastic over-molding capable of being sterilized.The stator in particular is entirely cast into plastic, whereby thisplastic also then forms the motor housing. In the end, there is providedthrough this a sheathing for the complete motor unit by which this isprotected effectively against the high temperatures and atmospherichumidity during the sterilizing process. A high performance plasticwhich is sold under the brand name PEEK has turned out to beparticularly preferred material for the realization of the plasticsheathing. This material also distinguishes itself due to its goodmaterial characteristics, especially also at high temperatures such asarise in sterilization, and is further hydrolysis resistant.

The use of the plastic housing then leads however to the issue that theplastic has a different thermal expansion coefficient than thesurrounding material of the handpiece sleeve. To avoid or reduce thestresses arising hereby between handpiece sleeve and plastic housing itis provided in accordance with a particularly advantageous developmentof the invention, that the motor is mounted in a special manner withinthe handpiece sleeve. In particular no fixed screwing together of themotor with the sleeve is provided but instead a sprung mounting isprovided. Through this a certain flexibility is created, whereby howeverthrough the spring force it is ensured that the motor is in principleurged with a substantially uniform force against a stop within the gripsleeve. The spring used for this thus compensates for correspondingdifferent expansions of the grip sleeve and the motor housing. Thisparticular mounting leads on the one hand to damage to the motor beingavoided, on the other hand it is ensured that the motor is arrangedpermanently in the same manner within the grip sleeve, which is ofadvantage to the extent that through this a very exact coupling withfurther power transmission elements of the drive is ensured.

Dental or dental-medical handpieces normally also have an illuminationarrangement via which the region to be worked in the mouth of a patientis illuminated during the use of the handpiece. Such a measure can beprovided also with the handpiece in accordance with the invention,whereby for this purpose preferably a light guide is used which extendsfrom the coupling elements of the handpiece up to a light exit point inthe forward end region. This light guide is configured in particular inone piece and extends thus continuously to the light exit point, wherebyit is taken past the motor, which is arranged preferably slightlyeccentrically within the grip sleeve. Further, media lines can extendthrough the handpiece which serve for the supply of air and/or water.Here, appropriate filter facilities can also be arranged within thehandpiece.

The invention will be explained in more detail with reference to theaccompanying drawings. There is shown:

FIG. 1 schematically an embodiment of the present invention in form of adental angled handpiece configured in accordance with the invention;

FIG. 2 a representation of the rotor of an electric motor arranged in ahandpiece in accordance with the invention;

FIG. 3 the configuration of the stator of the electric motor;

FIG. 4 a sectional illustration of the electric motor;

FIG. 5 the mounting of the electric motor within the handpiece sleeve;

FIGS. 6 and 7 details, to an enlarged scale, of the illustration of FIG.5;

FIGS. 8 and 9 a part section of the handpiece for clarification of thecourse of the media lines and a light guide;

FIG. 10 a further view of the media lines running along the handpieceand

FIG. 11 and 12 concepts for dental handpieces known from the state ofthe art.

The dental or dental-medical handpiece in accordance with the inventionwhich is illustrated schematically in FIG. 1 and provided overall withthe reference sign 1 has as main element an elongate grip sleeve 2. Inthe illustrated embodiment the handpiece 1 is constituted as a so-calledangled handpiece. The grip sleeve 2, constituted in one piece, has arearward region 2 b and a forward region 2 a which include with oneanother an angle a of about 155° to 170°, preferably of 162°. Thehandling of the handpiece 1 within the mouth of a patient is simplifiedby this configuration.

The head section of the handpiece 1 is located at the forward end of thegrip sleeve 2, which head section has a tool receiver 5 mountedrotatably by means of two bearings 6 a, 6 b. This tool receiver 5 has achuck, not illustrated in more detail, for the selective mounting of adental treatment tool which, set in rotation, is put to use for materialremoving working. The tool receiver 5 of the head section 3 is providedin particular for the rotatable mounting of dental drills. To furtherimprove the ergonomic qualities of the handpiece 1, the head section 3is further so configured in accordance with the invention such that thelongitudinal axis I of the tool receiver 5 includes with the axis II ofthe forward end region 2 b of the grip sleeve an angle β of about 100°.In comparison with classical configurations of angled handpieces, inwhich the drill is directed at a right angle to the grip sleeve, thispreferred form leads to a further improved handling.

At the rearward end the grip sleeve 2 is connected with the connectingpart 30 of a supply hose 31 which in particular leads to a supplyfacility (not illustrated) of a dental treatment station. Via thissupply hose 31 the handpiece 1 is provided with the required media foroperation, in particular current. This current is used—as explained inmore detail below—for the operation of the motor and could further beused also to provide illumination. Furthermore, however, also additionaltreatment media such as air and/or water can be provided, which can beused either individually or also as an air/water mixture which could beused for example for cleaning the surface to be worked. The media linesextending in addition through the handpiece 1 in this case are in thepresent case not illustrated in more detail, for reasons of simplicity.Their arrangement in the handpiece 1 will be is explained in more detailbelow. If such lines are present, also corresponding media filters canfurther be arranged in the handpiece 1.

The connection of the handpiece 1 is then effected via a couplingelement 4 situated in the rearward end of the grip sleeve 2, via which aconnection with the hose connection part 30 is effected. The connection,preferably configured as a bayonet coupling, can for example be soconfigured that the handpiece 1 is rotatable freely. As will beexplained in more detail below, the coupling in the illustratedembodiment is however so configured that there is a fixed orientationbetween handpiece 1 and hose connection part 30.

Dental handpieces can be in principle be configured with differentdrives. Classically, air or turbine drives or electrical drives are, forexample, put to use. A turbine thereby distinguishes itself due to itscompact manner of construction, on the other hand the operationalreliability is lesser in comparison with an electric motor. Further, incomparison with an electric motor the possibility of controlling thepower to be transmitted is available only to a restricted extent.

Electric motors have, however, to date the disadvantage that by theiruse the structure of the handpiece was enlarged. In the present casethere is now however put to use as electric motor a micromotor which ismounted completely within the grip sleeve 2 of the handpiece 1. Themotor, provided overall with the reference sign 10, has on the one handa stator 12 mounted in the handpiece sleeve fixedly, i.e. non-rotatably,and on the other hand a rotor 11 mounted rotatably with respect to thisstator 12 with the aid of two bearings 11 a and 11 b. The exactconfiguration of the motor 10 will be explained in more detail later. Itis of particular importance for the time being that the dimensions ofthe motor 10 are kept very compact, so that this is integrated into thegrip sleeve 2 completely. Here, it has to be taken into account inparticular that the grip sleeve 2 is configured in one piece or is of aplurality of parts which for the user are connected inseparably with oneanother, and correspondingly there arise no connection interfaces suchas arise with the known configurations in accordance with the state ofthe art. The electric motor 10 is correspondingly constituted for apermanent mounting within the handpiece sleeve 2 and forms a unit withthis, for which reason it is also sterilizable, to make possible aregular cleaning and sterilization of the handpiece 1 overall.

The rotation movement produced by the motor 10 is transferred to thetool receiver 5 by means of a shaft 15, which extends through theforward grip sleeve region 2 b. This shaft 15, which in turn is mountedrotatably by means of two roller bearings 16 a, 16 b, is for thispurpose coupled at its rearward end via a knee transmission 17 with therotor 11 of the electric motor 10; at the forward end a coupling iseffected between shaft 15 and tool receiver 5 by means of a headtransmission 18. The head transmission 18 can here in particular bringabout a reversal of direction of rotation, whereby the electric motor 10is then controlled preferably for counter-clockwise rotation, to bringabout the desired rotation of a drill held in the tool receiver 5. Seenoverall the handpiece in accordance with the invention thus has merelythree rotatably mounted axes or shafts (the motor rotor 11, theintermediate shaft 15 and the rotatable tool receiver 5 with theintegrated chucking system), in order to bring the drill or in generalthe tool into rotation by means of the voltage applied to the handpiece.This represents the ideal case whereby however—so far as necessary—alsointermediate transmission stages could be put too use. In turn thiswould lead, however, to greater requirements for space, for which reasonthe illustrated embodiment is particularly preferred. Further,theoretically, a planetary gear train also could be used for thetransmission of rotational speed (then with more axes of rotation).

Advantages of this particular configuration lie in that a very directpower transmission from the motor 10 to the tool receiver 3 is provided.The number of required mechanical components for motion transmission isclearly reduced in comparison with previous solutions. In turn this hasthe consequence that the production of the handpiece 1 can be simplifiedand made more economical and further also the handpiece 1 is overallrepair friendlier. In this connection, it has to be taken into accountthat in the dental industry for the working of tooth hard substancespeeds of rotation for the drill are needed in the region between120,000 rpm and 300,000 rpm. Angled pieces which are driven mechanicallyby a motor via transmission elements work to date predominantly in theregion of final speeds of rotation of 200,000 rpm, which is madepossible in that the speed of a classical drive motor of approximately40,000 rpm is translated by means of several transmission elements bythe factor 5 to the desired 200,000 rpm. Also translations by thefactors 3, 4 or 6 are occasionally in use. The transmission elementsrequired for such a high translation consist, however, of manycomponents which due to the high rotational speeds must be produced withthe highest precision, to keep undesired surface oscillations andacoustic noise emissions as small as possible. The required precisionand the number of components bring about high costs.

The, in contrast, direct power transmission present with the handpiece 1in accordance with the invention, and the use of very high speed ofrotation motors, now makes possible the use of transmissions in the caseof which the speed of rotation translation lies merely in the regionbetween 0.5 and 2, whereby despite everything the most varied ranges ofspeed of rotation and power ranges are available. Here it can inparticular be provided that the electric motor 10 works at speeds ofrotation in the region of 10,000 to 300,000 rpm, preferably of 75,000 to250,000 rpm or at maximum up to 250,000 rpm. The knee transmission 17and/or the head transmission 18 can then—so far as desired—havecorresponding translations in the region between 1:2 and 2:1. In theend, there can thus be achieved with this, without problem, final speedsfor the drill in a preferred region of 150,00 to 250,000 rpm or even upto 300,000 rpm, whereby use also in the lower motor speed range wouldalso however be conceivable. In this case it has to be ensured that themotor 10 provides a sufficient torque.

Further, the more direct power transmission with the handpiece 1 inaccordance with the invention leads, due to the less complextransmission gearings, also to a greater smoothness of running. Here ithas to be said that in dental technology speeds above 80,000 rpmnormally lead with regard to noise and vibration to considerableproblems, which in particular is then the case if the rotational speedtransmission takes place by means of a releasable coupling between aseparate motor part and the angled piece. These difficulties obviouslydo not arise with the solution in accordance with the present invention,which can be explained in particular in that the transfer of therotation movement is effected in each case by gear wheel pairings whichcannot be separated by the user. The particularly preferred arrangementof the head section 3 at an angle of about 100° with respect to theforward end region 2 b of the grip sleeve 2 can further be effectedwithout an additional mechanical reversal of the direction of rotation.Finally, the hygiene of the handpiece 1 is improved since the use ofvarious couplings can be omitted.

Through the complete integration of the micromotor 10 into the gripsleeve 2 the advantage is further obtained that the handpiece 1 canstill be kept very compact and has a handiness which is comparable withthat of a turbine handpiece. Thus the forward grip sleeve region 2 b canbe realized with a diameter of merely about 12 to 18 mm. The size of thehead section 3 also can be further reduced in comparison with knownsolutions. Through this a very precise drill guiding is made possible,which in the end leads to more exact working. The use of the electricmotor further also makes it possible to set the direction of rotation bya corresponding setting of the motor 10. In particular in the grindingof tooth replacements or similar elements advantages are hereby achievedsince a clockwise or counter-clockwise running can be set.

To improve further the possibilities for use of the handpiece 1, theavailability of an illumination can further be provided. For thispurpose, a light guide 20 extends longitudinally through the grip sleeve2, which light guide opens with its forward end in a light exit opening21. The forward end of the light guide 20 is thereby so directed thatthe light is approximately directed towards the forward end region of atool held in the tool receiver 5.

The light coupled into the light guide 20 originates from a lamp 32which is mounted in the hose connection part 30. Correspondingly thereis preferably provided a fixed orientation between handpiece 1 and hoseconnection part 30 such that the light of the lamp 32 can be coupled inan effective manner into the end face of the light guide 20 directed inan aligned manner. In this way an efficient illumination of the regionto be worked is made possible.

The integration of the electric motor 10 into the grip sleeve 2 of thehandpiece 1, which represents an significant point of the presentinvention, is also in particular supported by a special configuration ofthe motor 10, which will be described in more detail below withreference to FIGS. 2 to 4. To this end, FIG. 2 shows to an enlargedscale the exterior view of the rotor 11 of the motor 10, whilst FIG. 3shows the exterior view of the stator 12. FIG. 4 is in turn a sectionalview of the motor 10 in a state in which the rotor 11 is arranged withinthe stator 12.

The motor 10 is preferably, as already mentioned, a collectorless orbrushless dc motor with a permanent magnet rotor. Such so-called BLDC(Brushless Direct Current) motors distinguish themselves through theirhigh efficiency which is provided in particular also by a correspondingcontrol of the stator windings. Current supply of the stator windingsadapted to the disposition or the angular position of the rotor 11, theso-called commutation, is ensured by means of corresponding controlelectronics which permanently detect the position of the rotor 11 andcorrespondingly supply the windings with current of a suitable phase.Such an approach is already known in principle for BLDC motors andcorrespondingly will not be explained in more detail in the following.It is merely to be remarked that the possibility exists of detecting thedisposition of the rotor 11 either through the use of correspondingnon-illustrated sensors or through the development of the currentthrough the stator windings. The motor has a power of more than 10watts, in particular a power in the region between 10 and 30 watts.

Since in accordance with the present invention the motor 10 is to remainpermanently in the grip sleeve 2 of the handpiece 1, now howeverparticular measures must be taken which make possible a cleaning orsterilization of the handpiece 1 without the components of the motor 10thereby being damaged.

For this purpose, firstly it is provided that the permanent magnet ormagnets 40 of the rotor 11 illustrated in FIG. 2, which are normallyvery sensitive to corrosion, are specially coated, preferablynickel-plated. Such a coating protects the surfaces of the permanentmagnets 40, which are formed preferably by so-called rare earth magnets,from the hot vapors during the sterilizing process and provides that noparticular sealing of the motor 10 is required. The rotor magnet ormagnets 40 are thereby arranged according to the illustration inaccordance with FIG. 2 between two weighting rings 41, whereby theresulting arrangement, at the forward end of which the gear wheel 17 ais arranged for rotational movement transmission, is then mounted bymeans of two ball bearings 11 a and 11 b in the stator winding 12.

In turn the stator winding 12 also is constituted in a special manner,in order on the one hand to make possible a high efficiency of the motor10 and on the other hand the desired sterilizability.

With regard to the desired high efficiency of the motor 10, firstly ithas to be taken into account that a high efficiency and thus a slightheating only then can be achieved at the desired high rotational speedsif the no-load losses, which are caused by the rotating magnetic fieldof the rotor 11, are kept as slight as possible. These losses divideinto magnetic reversal losses and eddy current losses in the statorlamination. To keep these losses as slight as possible therefore, thestator 12 is realized from a plurality of laminations 42, arrangedbehind one another in an axial direction, which are of a nickel-ironalloy. On the one hand, this material distinguishes itself through arelatively high so-called saturation induction and on the other handthrough to a high specific electrical resistance. It is further decisivethat the laminations 42 used have an extremely slight thicknesspreferably of merely 0.1 mm, which enables the eddy current losses to bekept extremely slight.

For the protection of this arrangement the stator laminations 42 as wellas the windings 43 of the stator 12 are then embedded completely in awashable or sterilizable plastic 45, as can in particular be understoodfrom the sectional view in FIG. 4. By this encapsulation or sheathing45, within which the two bearings 11 a and 11 b are also arranged andfrom which merely the connections 44 for the windings 43 of the stator12 project rearwardly outwardly, a penetration of water or dirt into thewindings 43 is prevented. Further, the return path lamination of thestator 12 can in turn be protected against corrosion in special manner,for example with the aid of a corresponding coating. Especially thesensitive stator windings 43 as well as the stator laminations 42 can inthis way be protected in an effective manner. As can be understood fromthe illustration in FIG. 4, the plastic sheathing completely enclosesthese sensitive components of the motor 10. This plastic sheathingtherefore provides overall a protection for the motor 10 in form of amotor housing 46, since through this also the rotor 11 is enclosed tothe greatest extent. Merely by means of the two bearings 11 a, 11 b, atthe forward and rearward end of the rotor 11, could a slight componentof hot steam and other media penetrate into the interior of the stator12. The coating of the rotor magnet or magnets 40 then offers in thiscase however a sufficient protection during the washing or sterilizationprocess, so that no separate particular protection, e.g. a specialsealing the handpiece 1, is required.

The plastic PEEK is preferably used as material for the encapsulation orsheathing 45. This plastic, which is available both in readily flowingand in glass fibre reinforced variants, has proved to be particularlyadvantageous with regard to the desired sterilizability, since thismaterial has good material characteristic values also at hightemperatures and is further hydrolysis resistant.

Further, it has to be emphasized that the bearings 11 a, 11 b arefixedly integrated in the stator 12. The motor 10 correspondingly formsa compact physical unit. In this case the complete cooling air is passedthrough the air gap between rotor 11 and stator 12, wherein a part ofthe air can be led back on the outside over the stator, which leads to afurther cooling effect. The other part of the air in turn flows over thetransmission in the forward region of the handpiece 1 and exits here. Alubrication of the motor bearings 11 a, 11 b is also effected via theair gap. Seen overall there can thus be obtained an electric motor whichis kept very compact, with an extremely high efficiency.

The idea of realizing the housing 46 of the motor 10 by means of aplastic sheathing 45 with an injected stator 12 leads, however, to afurther issue which will be explained—with the solution thereof—in thefollowing.

Thus the housing 46 of the motor 10 in the handpiece 1 should not standpermanently under a too great a stress since otherwise it can come todamage in particular during sterilization, due to different thermalexpansions of the components. A rigid installation of the motor 10, forexample through corresponding screw connection of the components, wouldtherefore lead to difficulties because, due to the higher thermalexpansion coefficient of the plastic housing 46 with respect to steel,the axial stresses would increase upon heating. Since on the other handthe motor axis mounted in the motor housing 46 or the stator 11 must bepositioned very exactly due to the required high precision of the toothengagement of the coupling element 17, a special mounting of the motor10 in the handpiece sleeve 2 is proposed which can in particular beunderstood from the illustrations in FIGS. 5 to 7.

The solution of the problem described above consists in that the motorhousing 46 mounted in a cavity 50 of the grip sleeve 2 bears with itsforward end 46 a on a fixed stop 51 within the instrument sleeve 2. Atthe rearward end of the motor 10 there is present, in contrast, an airgap 52 to the coupling insert 4 fixedly screwed into the instrumentsleeve 2, whereby this air gap 52 can be understood in particular in therepresentation to an enlarged scale in FIGS. 6 and 7, in which only therear bearing 11 b is partly illustrated. At the coupling insert 4 thereis in turn arranged a plate spring 53 which bears axially on the onehand on the coupling insert 4, and on the other side bears on the outerring of the rearward ball bearing 11 b of the motor axis 11. This outerring directs the spring force of the plate spring 53 via a bond 54 intothe motor housing 46 which in this way is urged against the forward stop46 a of the instrument sleeve 2.

If it now comes for example to an expansion of the housing 46 due to awarming of the motor housing 46 for example during sterilization, thenthe plate spring 53 is slightly compressed. The axial force that acts onthe housing 46 however practically does not increase so that stressesduring the sterilizing process can be reduced. The air gap 52 is therebydimensioned such that it can take up the expansion occurring without themotor housing 46 standing on the coupling insert 4. In combination withthe measures for the configuration of the motor 10 described above theresult is provided that the motor 10 is protected in extremely effectivemanner on the one hand against external influences and on the other handis reliably permanently mounted within the handpiece sleeve 2. Thereby,the mounting is in particular such that the correct arrangement of themotor axis, in particular of the coupling element 17 b, with respect tothe gear wheel of the forward drive shaft 15 is permanently ensured.

As already mentioned above, the motor 10 configured in accordance withthe invention also distinguishes itself in particular due to its compactarrangement within the handpiece sleeve 2. This makes it possible topass additional lines through the sleeve, to make available cleaning orcooling mediums required during treatment. In accordance with theillustrations in FIGS. 8 to 10 it is provided in particular that themotor 10 is arranged slightly eccentrically within the sleeve andcorresponding media lines 22, 23 are firstly led past the underside ofthe motor housing 46 and then led to the handpiece head 3. These medialines 22, 23 serve in particular for the supply of air and water,whereby also the possibility is provided of issuing both media at thesame time in the form of a spray. Between the two media lines there isfurther carried the above-mentioned light guide rod 20 which extendsfrom the coupling part 4 up to the forward light exit 21 and makespossible an illumination of the region being worked. The mentionedeccentric arrangement of the motor 10 is thus in particular of advantageif a plurality of lines run in the handpiece sleeve 2. In case, however,that a delivery of light and spray media is not provided and noaccompanying lines or light guides correspondingly run in the handpiece,the motor 10 could of course also be arranged centrally within thesleeve 2.

In the end, there is thus provided a handpiece which has clearadvantages over previous handpieces having electric motors with regardto its dimensions, its handling and its operational characteristics.Through this, further possible applications are provided for thehandpiece since the high speed drive can be used also for example forapplications in the ENT field, in microsurgery or in minimally invasivetreatments.

1.-30. (canceled)
 31. A sterilizable dental handpiece comprising: anelongate tubular member having a proximal end having a first couplingmember adapted to connect to a second coupling member supplyingelectrical power and fluid under pressure to the handpiece, and a distalend having a tool receiver for detachably holding a dental tool in thehandpiece; a brushless electric motor in the tubular member toward theproximal end comprising a stator having electric windings, and a rotorcomprising a central axial shaft and permanent magnets carried on theshaft; the stator being positioned in an annular chamber in the tubularmember and being sealed to protect the stator windings against exposureto moisture and contaminants; an electrical lead extending from thefirst coupling member at the proximal end of the tubular member into thechamber to conduct electrical power to the stator windings; bearingsmounting the rotor for rotation within and relative to the stator andsecuring the rotor against axial movement within the tubular member; anda drive transmission toward the distal end of the tubular member mountedfor rotation within the tubular member and connecting an end of therotor to the tool receiver for rotating the tool receiver when the motoris activated; wherein the motor and transmission are fixedly mountedwithin the handpiece with the handpiece presenting an end for connectionto both sources of supply of electrical power and of fluid to thehandpiece for reducing the length and weight of the handpiece for easeof use.
 32. The sterilizable dental handpiece of claim 31, wherein themotor comprises a rotating region and a static region receiving thestator windings, the static region of the motor being moved over andsurrounding the rotating region of the motor when the motor is insertedinto the internal chamber for enabling the motor to integrate completelyinto the internal chamber of the handpiece.
 33. The dental handpiece ofclaim 31, wherein the motor comprises a rotating region and a staticregion receiving the stator windings, wherein the stator is cast into asheathing.
 34. The dental handpiece of claim 33, wherein the statorsheathing forms the motor housing.
 35. The dental handpiece of claim 34,wherein the stator sheathing is formed of a material capable ofwithstanding sterilization temperature and humidity.
 36. The dentalhandpiece of claim 31, wherein the motor is completely integrated intothe grip sleeve such that the motor forms a unit with the grip sleeve.37. The dental handpiece of claim 31, wherein the tool receiver isconfigured for mounting a tool that is to be set into rotation.
 38. Thedental handpiece of claim 31, wherein the tool receiver is connected tothe motor via a shaft that extends through the forward region of thegrip sleeve.
 39. The dental handpiece of claim 38, wherein the shaft iscoupled with a motor shaft via a knee transmission.
 40. The dentalhandpiece of claim 39, wherein the shaft is coupled with the toolreceiver via a head transmission at a forward end of the shaft.
 41. Thedental handpiece of claim 40, wherein the head transmission isconfigured to enable a reversal of direction of rotation.
 42. The dentalhandpiece of claim 31, wherein a rotor of the motor includes a corrosionresistant coating.
 43. The dental handpiece of claim 31, wherein thetubular member comprises a sleeve at an outer surface thereof, and themotor is spring mounted within the sleeve and is biased against aforward stop formed in the sleeve.
 44. The dental handpiece of claim 31,further comprising at least one coupling element and one light guide,the light guide extending from the coupling element to a light exitpoint.
 45. The dental handpiece of claim 31, further comprising a supplyhose for providing fluid media required for operating the handpiece. 46.The dental handpiece of claim 31, wherein the motor is a brushlessmotor.
 47. An electric motor for use in a sterilizable dental handpiece,the motor comprising: a collectorless dc motor sized to fit completelyinside the dental handpiece said motor comprises a stator; a rotorconnected to the motor and having at least one permanent magnet; asheathing for surrounding the motor and the rotor to protect the motorand rotor against exposure to contaminants; a corrosion resistantcoating applied to the permanent magnet to prevent the magnet fromcorroding; and the stator of the motor comprising a package made oflaminations arranged behind one another in an axial direction.
 48. Theelectric motor of claim 47, wherein the sheathing is formed from a PEEKplastic material.